The Growtgh Of Near-Stoichiometric LiNbO₃ And Nd³⁺ Doped LiNbO₃ Crystals Using Bridgman Method

Lithium niobate is well known as a multi-functional crystal,which has been extensively used in solid-state lasers,opto-electronic devices and high resolution holographic storage due to its excellent property.But the congruent LiNbO₃ presents a low threshold for photorefractive damage because of Li deficiency(Li/Nb=0.946) which has been hold up its widely application.By means of the optimum conditions such as proper feed materials,sealed platinum crucibles,growth rate of 0.8-1.2mm/h,the temperature gradient of 40-60℃/cm across the solid-liquid interface and adding K₂O as flux,the near-stoichiometric Lithium niobate single crystal and Nd³⁺ doped LiNbO₃ were obtained by Bridgman method.The structure,composition and optical properties of the crystals were characterized.The absorption,emission and fluorescence lifetime are also measured.Based on the Judd-Ofelt theory, we obtained the optical parameters of the crystal such as the luminescent quantum efficiency,the radioactive lifetimes,the branching ratios and the emission cross-section.The calculated phenomenological intensity parameters are as follows:Ω₂=4.05×l0^-20cm²,Ω₄=2.71×l0^-20cm²,Ω₆=4.27×l0^-20cm².Resulting from the Judd-Ofelt theory,the most important transition ³F_3/2→⁴I_11/2 which is of 1096 nm has the maximal fluorescent ratiosβof 0.52,radiative transition rates A of 1189.3 s^-1 and the emission cross-section o _em of 1.02×10^-20cm².The fitted lifetimeÏ„_exp is 240μs,the calculated irradiative lifetimeÏ„_r is 436μs,so the luminescent quantum efficiency of³F_3/2 is about 55%.